1. Field of the Invention
The present invention relates to a computer system and a method for controlling interface commands of a disk apparatus for online data migration technology of the disk apparatus and, more particularly, to migration technology for the contents of the disk apparatus for storing task process data while a host computer continues to process task data.
2. Description of the Related Art
Conventionally, in the case of updating a newly connected disk apparatus (new disk apparatus) from a disk apparatus (old disk apparatus or migration source disk apparatus) functioning as an outside storage device, in order to utilize continuously data that are processed up to now, data of the old disk apparatus shall be moved to the new disk apparatus (migration). In such a case, as a conventional general method, a method of storing the contents of the current disk apparatus once in a backup file of a tape unit or the like and then restoring after the disk apparatus was exchanged has been employed. Otherwise, there has been known a method for connecting the new disk apparatus, as well as a conventional old disk, to a host computer and then storing copy data of the old disk apparatus in the new disk apparatus by the host computer. Here, these methods stop the tasks of the host computer for a long period of time. Operation for stopping tasks for such a long period of time cannot be accepted as the tasks of the most modern data center characterizing non-stop operation.
For a method for improving such a condition, a patent document 1 (Japanese published unexamined patent application No. 2001-249853) discloses a method for executing data migration from the old disk apparatus to the new disk apparatus by connecting the new disk apparatus to a switch provided between the host computer and the old disk apparatus. According to this data migration method, a unit for copying data from the old disk apparatus to the new disk apparatus while the disk apparatus of the host computer is continuously accessed is provided in the switch (or a storage system). However, in this data migration method, the old disk apparatus and the host computer that is used are necessarily disconnected for a while and then the switch having the above cited online data migration function shall be provided. Here, if the number of access paths between the host computer and the old disk apparatus is one, the computer system shall be halted.
For another method, a patent document 2 (Japanese published unexamined patent application No. 11-184641) discloses a method for executing data migration without stopping while plural access paths are included between the host computer and the disk apparatus and at least one access path is continuously maintained. This data migration method is made and used by a changing-over path function provided on the host computer, i.e., a method for changing-over access paths dynamically by managing two or more access paths between the host computer and the disk apparatus on the host computer. The changing-over path function of the host computer, however, may not work properly for a disk apparatus having different interface specification as a process task of a specified disk apparatus. The reason is because a SCSI response of the disk apparatus is utilized inherently in order to identify automatically plural access paths for the disk apparatus (referred to a logical unit in the SCSI code). Namely, for such a response, there may be caused a problem in which access is denied if consistency is not recognized in disk inherent information for an interface command.
[Patent document 1]    Japanese published unexamined patent application No. 2001-249853
[Patent document 2]    Japanese published unexamined patent application No. 11-184641